With the miniaturization of electronic products such as mobile phones, laptops, hearing aids and so on, it is required that the sizes of parts used in such devices should be getting smaller and smaller, thus, a miniature microphone having small size, high quality and shielding structure is getting well received by electronic device manufacturers day by day.
For example, a condenser microphone with a shielding function was disclosed in Chinese patent application publication No. CN1909746A (hereinafter, the “746 publication”). As shown in the perspective view of FIG. 1 and the cross-sectional view of FIG. 2 (also the FIG. 1 and FIG. 2 of the “746 publication”), the condenser microphone 10 mainly includes a frame-like body 12, a circuit substrate 13, a contact spring 14, a backplate 15, a spacer 16, a diaphragm 17, a diaphragm plate 18 and a cover 19. The frame-like body 12 comes to be the skeleton of the condenser microphone 10, it has a film-like electrically conducting layer 12b configured on the concave surfaces 12a formed on the outer lateral sides of the frame-like body 12, and has a upper conducting layer and a lower conducting layer formed respectively on the upper surface and the lower surface thereof. The frame-like body 12 is electrically connected to the cover 19 through the upper conducting layer, and is electrically connected to the ground side electrodes on the circuit substrate 13 through the lower conducting layer. Thus, the cover 19, the frame-like body 12 and the circuit substrate 13 form the casing of the condenser microphone, so that the circuits inside the frame-like body 12 are electromagnetically shielded.
Meanwhile, there is also disclosed a method of manufacturing the frame-like body 12 of the above-mentioned condenser microphone in the “746 publication”. First, a plurality of holes 22, which are required for manufacturing the frames, are laterally and longitudinally formed at prescribed intervals on a circuit board substrate. Then, a plurality of long holes 30b, 30c, which are used to form a concave surface 12a and a conducting layer 12b, are formed at prescribed intervals around the holes 22. Thereafter, the long holes 30b, 30c are filled or coated with a conductive adhesive or conductive paste to form the conducting layer 12b. Finally, the long holes 30b, 30c are cut along the central lines thereof so as to obtain the frame-like body 12 having the surfaces on the outer lateral sides thereof configured with conducing layers.
However, there exist the following disadvantages in the above method of manufacturing the frames: (1) when the holes and the long holes required for the frames are processed, a CNC processing such as punching, drilling, or milling is usually employed, which results in a complicated machine process; (2) the long holes which are needed to be processed around the frames inevitably take up the space of the substrate, thereby reducing the material utilization.
If the conducting layer playing an electromagnetic shielding role is configured on the inner lateral sides of the frame, a problem will raise that the conducting layer is easy to come into contact with the electronic elements inside the frame and causes a short circuit, although the problems mentioned in the previous paragraph may be partially solved.